1. Field of the Invention
The present invention relates to a cooling water circuit system which improves cooling effect for cooling water-cooled engine mounted on a vehicle in the summer while improving heating effect of a passenger compartment of the vehicle in the winter.
2. Description of Related Art
In a conventional heating apparatus described in JP-A-9-272327 by the applicant of the present invention, a heater core, a heat accumulating tank and an electrically-driven water pump are provided in a cooling water circuit, and a valve is provided to control amounts of cooling water flowing into a water-cooled engine, the heater core and the heat accumulating tank. When a heating mode is set when the engine is stopped, the electrically-driven water pump and the valve are operated so that cooling water circulates only between the heat accumulating tank and the heater core. Thus, even when the engine is stopped, air passing through the heater core is heated in the heater core by using high-temperature cooling water from the heat accumulating tank as a heating source.
However, in the conventional heating apparatus, because flow resistance of cooling water in the cooling water circuit becomes larger by providing the heat accumulating tank, it is necessary to operate the water pump with a high power. Further, because the cooling water circuit of the heating apparatus becomes complex by the heat accumulating tank, the valve for switching cooling water flow and a control circuit of the valve are also necessary, and the heating apparatus is produced in high cost.